What Can We Learn About Endangered Humpback Chubs From Threatened Flannelmouth Sucker Otolith Microchemistry in Grand Canyon?

An adaptive management program is underway in the Colorado River below the Glen Canyon Dam in Grand Canyon, Arizona USA. As part of this program, resource managers are developing dam operations which aid in the protection and restoration of key Colorado River resources, including native fishes. The native fish community in this reach of river historically supported eight species, but only four remain, of which one (humpback chub, Gila cypha) is listed as endangered under the US Endangered Species Act. Humpback chub have been extensively studied in Grand Canyon using non-lethal methods to assess abundance, movement, and habitat use. Limited studies have been conducted on the other native species, including flannelmouth sucker (Catastomus latipinnis), primarily because these species are not thought to be imperiled. We used otolith microchemistry techniques to assess provenance, movement, and growth patterns of flannelmouth sucker to expand our knowledge on the basic ecology of this species and compare this information to humpback chub data. If differences in the ecology of these species could be identified this might help to explain why flannelmouth sucker populations have likely not declined as extensively as humpback chub, and inform future management in Grand Canyon.